This invention relates to a system for reporting alarms at remote premises to a central station and, more particularly, to the reporting of plural parallel bits of information via a tone transmission.
Central station systems have arisen to meet the needs of those commercial and residential establishements which are not large enough to provide their own alarm systems and security forces. Two forms of alarm reporting in central station applications were developed to service these remotely located customers. In the first or direct wire service, the alarm sensors for detecting such occurrences as unauthorized door openings, breakage of windows, and fires, were connected to a pair of telephone lines, dedicated specifically to that customer and extending to the central station. In the second or McCulloh service, a plurality of customers shared a common telephone line with sensors located at strategic points in each of the customers' premises and alarms occuring at any of the customers premises were reported in a coded format to identify the specific customer at which the alarm arose.
In both types of systems, an operator located at the central station monitored the signals received from the remote customer premises. If the current level on the dedicated wires in the direct wire system changed by greater than a specified percentage, an alarm for that remote premises would be given. In the McCulloh type system, if a code was received identifying a specific customer premises, again that remote customer premises was in alarm. In either case, the operator would contact the proper authorities to eliminate the condition which gave rise to the alarm.
These prior art type systems involved not only a complex communication network between the remote premises and the central station but also required complex equipment at the central station to process the information coming both over a multitude of inputs and in either the direct dedicated wire or the McCulloh formats. The Bell Systems are now providing a communication network which eliminates the duality of providing both direct dedicated wire and McCulloh systems and reduces the complexity of the communication system. The present invention is designed to use the Bell Systems equipment in a central station application for reporting alarms at remote premises to a central station and for providing certain control functions at the remote premises by messages generated at the central station.